1. Field of the Invention
The invention relates to a device for comminuting input.
2. Description of the Background Art
Comminution devices are used primarily for comminution of input material by impact or striking, wherein comminution down to very fine grinding is possible. For example, devices of this class are used in the food industry for fine grinding of fat-containing beans, such as cacao or coffee, or beating and homogenizing fruit pulps. In the chemical industry, devices of this class are used, for example, for producing pigments or grinding polymers. The comminution of soft-elastic materials such as rubber or used tire granules is also possible, generally in conjunction with the introduction of cooling power before the grinding process, for example by supplying liquid nitrogen to make the input material brittle.
Pin mills are known with disks disposed coaxially inside a housing and at a distance from one another, wherein one rotates or both rotate with differential speeds. The disks have comminuting pins on the disk surfaces facing one another, which overlap in the space between the disks in the axial direction. In this process, the comminuting pins of each disk sit on circumferential circles moving concentrically relative to the axis of rotation, wherein the radii of the circumferential circles of one disk differ from those of the other disk to permit mutual combing of the opposing comminuting pins during rotation. The input material is introduced axially to such pin mills through a central opening in one of the disks and deflected in the radial direction by impact on the other disk so that it flows radially through the comminution zone formed by the comminuting pins and is withdrawn after its emergence from the comminuting gap formed by the disk. A machine of this type is described, for example, in DE 27 13 809, which corresponds to U.S. Pat. No. 4,152,081.
A characteristic feature of the pin mills known from the conventional art is their annular disk shaped comminution zone, which extends in a radial plane relative to the axis of rotation, thus has a two-dimensional form. The comminution zone is thus passed through radially, wherein the material particles are driven radially outward both by the entrainment force of the carrier gas stream and by the centrifugal force induced by the circular motion. Therefore, the material to be comminuted wanders through the comminution zone relatively rapidly, so that the action time available to the comminuting pins for breaking down the input material is relatively brief.
This type of construction further means that for the comminuting pins necessary for comminution, only the opposing disk surfaces are available, which considerably limits the number of comminuting pins. In addition, as a result of the radial minimum distance between the comminuting pins that is to be maintained, the play for the arrangement of the comminuting pins is further limited. As a result, in known mills, the density of the comminuting pins is not particularly high, and thus the performance capability of such pin mills is limited.
Since the comminuting pins are disposed upon different circumferential circles relative to the axis of rotation, the comminuting pins disposed on the outer circumferential circles rotate with a higher circumferential velocity than those located further inside. Thus the comminuting pins, depending on their radial difference from the axis of rotation, strike the material to be ground with different energy, entailing the risk that the fine-ground end product displays a greater dispersion in degree of fineness.